1. Technical Field
The invention is related to the protection of computer mass memories such as magnetic hard disk drives, optical disk drives and the like, and in particular to apparatus for protecting key sectors of such memories from accidental or unauthorized overwriting.
2. Background Art
A computer is vulnerable to accidental or unauthorized overwriting or erasure of portions of its mass memory containing key programs such as the operating system, for example, or containing important archival storage such as accounting information, for example. Unauthorized overwriting can occur when a computer virus somehow enters the computer in the form of a clever program that gets stored in the mass memory and which contains instructions causing the computer to overwrite such key portions of its mass memory. If, for example, a portion of the mass memory containing the operating system is overwritten because of such a virus, the computer does not function the next time it is powered up. If portions of the mass memory containing application programs are overwritten, such programs will not run properly. Accidental or unauthorized overwriting of the mass memory can also occur by accidental formatting of the hard drive or by erasing sector zero of the mass memory including the file allocation table.
An object of the present invention is to provide a computer which is impervious to unauthorized (intentional) or accidental overwriting of key sectors of its mass memory. A related object of the invention is that the computer be impervious to such unauthorized or accidental overwriting of key mass memory sectors even in the presence of an active computer virus in the mass memory.